The synthesis of several titanium-iron multiply bonded complexes supported by a 2-(diphenylphosphino)pyrrolide (NP) ligand is reported. Treatment of the homoleptic, 8-coordinate Ti(NP)4 monometallic precursors with FeCl2 and KC8 yielded the tetragonally-symmetric heterobimetallic complex Ti(μ2-NP)4Fe, 2. X-ray crystallographic analysis reveals a short metal-metal distance (2.021(2) and 2.028(2) Å for two independent molecules in the asymmetric unit) consistent with a Fe-Ti triple bond. Theoretical calculations also indicate 3 bonding interactions. Further reduction of 2 by 2 electrons with KC8 results in the isolation of the dianion, [K2][(κ1-NP)Ti(μ2-NP)3Fe], 3, where one phosphine arm has decoordinated from Fe, and the Fe-Ti triple bond has shortened to 1.9474(7) Å. This shortening results from the local ligand field change about Fe from tetragonal to trigonal, which allows for significantly better orbital overlap with Ti.
Bibliographical noteFunding Information:
Financial support was provided by the University of Minnesota (start up funds) and the ACS Petroleum Research Fund (ACS-PRF 54225-DNI3). Victor G. Young, Jr. is thanked for assistance with X-ray diffraction data interpretation. The Bruker-AXS D8 Venture diffractometer was purchased through a grant from NSF/MRI (1224900) and the University of Minnesota. Equipment purchases for the NMR facility were supported through a grant from the NIH (S10OD011952) with matching funds from the University of Minnesota. R.K.C. thanks the National Science Foundation for a Graduate Research Fellowship under Grant No. 00039202.
© 2016 Elsevier B.V.
- Inorganic synthesis
- Iron complexes
- Metal-metal multiple bonds
- Pyrrolide ligands
- Titanium complexes